Got to replacing a blown airbag but I got 2 different units. Does anyone know what colour does what? On one, the brown is connected to the gas canister and the black connected to the body as earth (makes sense), on the other, the brown is connected to the body, the black is the canister. Any ideas?

I doubt it matters which as it is all dc however I would wire it as your old one just in case. You will need to replace the air bag computer also, if you have the light on the dash, it is by the gear stick under the center console